Pope Francis made renewed calls on Easter Sunday for an immediate ceasefire in Gaza and the release of all Israeli hostages in a peace-focused address marking the most important day on the Christian calendar.

Francis presided over Mass in a packed St Peter's Square, and then delivered his "Urbi et Orbi" (to the city and the world) blessing and message from the central balcony of St. Peter's Basilica.

Francis, 87, has been in poor health in recent weeks, forcing him on repeated occasions to limit his public speaking and cancel engagements as he did on Good Friday, skipping at short notice a procession at Rome's Colosseum.

However, he took part normally in other Holy Week events leading up to Easter, and appeared in relatively good spirits at Sunday's Mass. Easter celebrates the day in which the faithful believe Jesus rose from the dead.

After the service, the pontiff took to his open-topped popemobile to tour the square and the avenue connecting the Vatican to the River Tiber and greet the tens of thousands of people who had lined up to see him.

Francis has repeatedly deplored the death and destruction in the Gaza war.

"I appeal once again that access to humanitarian aid be ensured to Gaza, and call once more for the prompt release of the hostages seized on last October 7 and for an immediate ceasefire in the Strip," he said on Sunday.

"How much suffering we see in the eyes of children, the children have forgotten to smile in those war zones. With their eyes, children ask us: Why? Why all this death? Why all this destruction? War is always an absurdity and a defeat", he added.